Journal of Environmental Sciences - Volume 18, issue 2

Authors: GUO, Zhao-hai | YANG, Min | ZHANG, Yu | PEI, Yi-shan | ZHANG, Jing-song | FAN, Jie | HIROTSUJI, Junji

Article Type: Research Article

Abstract: The effectiveness of preozonation was evaluated on treating a bromide-bearing dam source water in south China through batch-scale experiments. Preozonation at ozone doses of 0.5–1.0 mg/L (at ozone consumption base) enhanced total organic carbon (TOC) removal through coagulation, and resulted in an almost linear reduction of ultraviolet absorbance at 254 nm (UV_{254} ). The removals of TOC (after coagulation) and UV_{254} at the ozone dose of 1.0 mg/L were …36% and 70%, respectively. Preozonation at an ozone dose between 0.5 and 1.0 mg/L resulted in the removal of disinfection byproducts formation potential (DBFP) including trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP) for about 50%. The removals of THMFP and HAAFP decreased with the further increase of ozone dose. Ozonation of bromide-bearing water (bromide concentration, 34μg/L) produced a bromate concentration under the detection limit (2μg/L) at ozone doses <1.5 mg/L. However, bromate <10 μg/L could be produced when the bromide concentration was increased to 96μg/L. Show more

Keywords: ozone, drinking water, preozonation, disinfection byproducts formation potential (DBFP), bromate formation

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 209-213, 2006

Authors: SHI, Bao-you | TANG, Hong-xiao

Article Type: Research Article

Abstract: Compared with traditional aluminum salts, polyaluminum chloride (PACl) has better coagulation-flocculation performance in turbidity removal. However, it is still inferior to organic polymers in terms of bridging function. In order to improve the aggregating property of PACl, different composite PACl flocculants were prepared with various organic polymers. The effect of organic polymer on the distribution of Al (III) species in composite flocculants was studied using ^{27} Al NMR and Al-ferron complexation …methods. The charge neutralization and surface adsorption characteristics of composite flocculants were also investigated. Jar tests were conducted to evaluate the turbidity removal efficacy of organic polymer modified composite flocculants. The study shows that cationic polymer and anionic polymer have significant influences on the coagulation-flocculation behaviors of PACl. Both cationic and anionic polymers can improve the turbidity removal performance of PACl but the mechanisms are much different: cationic organic polymer mainly increases the charge neutralization ability, but anionic polymer mainly enhances the bridging function. Show more

Keywords: polyaluminum chloride (PACl), organic polymer, composite flocculant

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 214-220, 2006

Authors: HE, Lian-sheng | LIU, Hong-liang | XI, Bei-dou | ZHU, Ying-bo

Article Type: Research Article

Abstract: Livestock wastewater has been a major contributor to Chinese cultural eutrophication of surface waters. Constructed wetlands are under study as a best management practice to treat wastewater from dairy and swine operations, but the removal efficiency of pollutants is relatively low. Enhancing the treatment efficiency of livestock wastewater by effluent recirculation was investigated in a pilot-scale vertical-flow constructed wetland. The wetland system was composed of downflow and upflow stages, on which narrow-leaf …Phragmites communis and common reed Phragmites Typhia are planted, respectively; each stage has a dimension of 4 m^2 (2 m × 2 m). Wastewater from facultative pond was fed into the system intermittently at a flow rate of 0.4 m^3 /d. Recirculation rates of 0, 25%, 50%, 100% and 150% were adopted to evaluate the effect of the recirculation rate on pollutants removal. It shows that with effluent recirculation the average removal efficiencies of NH_4 -N, biological oxygen demand (BOD_5 ) and suspended solids (SS) obviously increase to 61.7%, 81.3%, and 77.1%, respectively, in comparison with the values of 35.6%, 50.2%, and 49.3% without effluent recirculation. But the improvement of TP removal is slight, only from 42.3% to 48.9%. The variations of NH_4 -N, dissolved oxygen (DO) and oxidation-reduction potential (ORP) of inflow and outflow reveal that the adoption of effluent recirculation is beneficial to the formation of oxide environment in wetland. The exponential relationships with excellent correlation coefficients (R^2 >0.93) are found between the removal rates of NH_4 -N and BOD_5 and the recirculation rates. With recirculation the pH value of the outflow decreases as the alkalinity is consumed by gradually enhanced nitrification process. When recirculation rate is kept constant 100%, the ambient temperature appears to affect NH_4 -N removal, but does not have significant influence on BOD_5 removal. Show more

Keywords: vertical-flow, constructed wetland, swine wastewater, effluent recirculation, recirculation rate, nitrification

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 221-226, 2006

Authors: ZHU, Jing-ping | HU, Yong-you | LIANG, Hui-qiang

Article Type: Research Article

Abstract: The feasibility of the nitrous organic wastewater treated was studied in seven anaerobic sequencing batch reactors (ASBRs) (0^# –6^# ) which had been run under stable anaerobic ammonium oxidation (Anammox). By means of monitoring and data analysis of COD, NH_4^+ -N, NO_2^- -N, NO_3^- -N and pH, and of microbial test, the results revealed that the optimal Anammox performance was achieved from 2^# reactor in …which COD/NH_4^+ -N was 1.65, Anammox bacteria and denitrification bacteria could coexist, and Anammox reaction and denitrification reaction could occur simultaneously in the reactors. The ratio of NH_4^+ -N consumed: NO_2^- -N consumed: NO_3^- -N produced was 1:1.38:0.19 in 0^# reactor which was not added glucose in the wastewater. When different ratio of COD and NH_4^+ -N was fed for the reactors, the ratio of NO_2^- -N consumed: NH_4^+ -N consumed was in the range of 1.51–2.29 and the ratio of NO_3^-<FORMULA>-N produced: NH<FORMULA>_4^+ -N consumed in the range of 0–0.05. Show more

Keywords: anaerobic ammonium oxidation (Anammox), anaerobic sequencing batch reactor (ASBR), biological denitrification, denitrification

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 227-231, 2006

Authors: KONG, Ling-yu | ZHANG, Xiao-jian | WANG, Zhan-sheng

Article Type: Research Article

Abstract: A study on advanced drinking water treatment was conducted in a pilot scale plant taking water from conventional treatment process. Ozonation-biological activated carbon process (O_3 -BAC) and granular activated carbon process (GAC) were evaluated based on the following parameters: COD_{Mn} , UV_{254} , total organic carbon (TOC), assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). In this test, the average removal rates of COD_{Mn} , UV_{254} …and TOC in O_3 -BAC were 18.2%, 9.0% and 10.2% higher on (AOC) than in GAC, respectively. Ozonation increased 19.3–57.6 μg Acetate-C/L in AOC-P17, 45.6–130.6μg Acetate-C/L in AOC-NOX and 0.1–0.5 mg/L in BDOC with ozone doses of 2–8 mg/L. The optimum ozone dose for maximum AOC formation was 3 mgO_3 /L. BAC filtration was effective process to improve biostability. Show more

Keywords: ozonation, biological activated carbon, COD_{Mn}, UV_{254}, TOC, AOC, BDOC, biostability

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 232-235, 2006

Authors: HUANG, Hong | OU, Wen-hua | WANG, Lian-sheng

Article Type: Research Article

Abstract: The concentrations of semivolatile organic compounds, organochlorine pesticides and heavy metals in sediments from Jiangsu reach of Huaihe River, China, were presented. The organic compounds were extracted by acetone: n-hexane using a Soxhlet apparatus and concentrations were performed using HP6890 gas chromatography coupled by FID and ECD detector. The total contents of 8 heavy metals by inductively coupled plasma atomic emission spectrometry or cold-vapor/atomic absorption spectrometry were developed. 30 semivolatile organic compounds …were detected, including substituted benzenes, phenols, phthalates and polycyclic aromatic hydrocarbons, from 0.01 to 3.01 mg/kg. 16 organochlorine pesticides were almost detected and from 0.010 to 2.339 μg/kg. Concentrations of major metals were 50 mg/kg or less, mean level of mercury was only 0.055 mg/kg. Compared to sediment quality guidelines (SQGs), concentrations of some semivolatile organic compounds were high enough to cause possible toxic effects to living resources. The organochlorine pesticides presented relatively low, lower than threshold effect concentrations (TECs), harmful effects on sediment-dwelling organisms were not expected. Chromium posed probable toxic effects to the living resources, other heavy metals had no threat temporarily according to SQGs. Show more

Keywords: sediment, semivolatile organic compounds, organochlorine pesticides, heavy metals, sediment quality guiedlines, Huaihe River

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 236-241, 2006

Authors: HE, Sheng-bing | XUE, Gang | KONG, Hai-nan

Article Type: Research Article

Abstract: In this study, the effect of zeolite powder addition on submerged membrane bioreactor (SMBR) on membrane permeability, and the removals for COD, NH_3 -N, TN were investigated. Through the parallel operation of control and test systems, it was found that the zeolite powder addition could alleviate the ultra-filtration membrane fouling and enhance the membrane permeability. On the basis of experimental investigations, a concept of "protection coating layer" was proposed to illustrate the phenomenon of UF …membrane fouling. In addition, the removal for COD in test system was more stable, a little higher compared to the control system. Due to the combination of nitrification and ion exchange, a more excellent removal for NH_3 -N in test system was obtained regardless of influent NH_3 -N loading rate. It was also found that a mean 25% higher TN removal took place in the test system, and ion exchange and simultaneous nitrification and de-nitrification were analyzed to be main factors. During the stable operation period, the SOURs of test pectively zeolite powder added sludge and control activated studge were measured to be 75mgO_2 /(gML VSS·h) and 24 mgO_2 /(gML VSS·h) respectively, it meant that the zeolite powder addition could enhance the microorganism activity significantly. Show more

Keywords: submerged gravitation-filtration membrane bioreactor, performance, zeolite powder, membrane fouling, microorganism activity

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 242-247, 2006

Authors: SUN, Xing-bin | CUI, Fu-yi | ZHANG, Jin-song | GUO, Zhao-hai | ZHAO, Kai | LIU, Li-jun | LV, Wei-min

Article Type: Research Article

Abstract: Chironomid larvae propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfection process like chlorination due to its stronger resistance to oxidation. In this paper, a pilot-scale study of chlorine dioxide preoxidation cooperating with routine clarification process for Chironomid larvae removal was conducted in Shenzhen Waterworks in Guangdong Province, China. The experimental results were compared with that of the existing prechlorination process in several aspects, including …the Chironomid larvae removal efficiencies of water samples taken from the outlets of sedimentation tank, sand filter, the security of drinking water and so on. The results showed that chlorine dioxide might be more effective to inactivate Chironomid larvae than chlorine and Chironomid larvae could be thoroughly removed from water by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated water by chlorine dioxide preoxidation were evidently less than that ofprechlorination and the mutagenicity of drinking water treated by pre-dosing chlorine dioxide was substantially reduced compared with prechlorination. Show more

Keywords: Chironomid larvae, chlorine dioxide, chlorine, preoxidation, water treatment

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 248-253, 2006

Authors: YUAN, Shou-jun | ZHENG, Zheng | MU, Yan-yan | YU, Xin | ZHAO, Yong-fu

Article Type: Research Article

Abstract: Radiation-induced reduction of chromium(VI) (Cr(VI) by γ-irradiation was studied with an initial concentration of 42 mg/L in aqueous solutions. Several factors which might affect the reduction of Cr(VI) to Cr(III) were examined. pH of aqueous solution affects the reduction efficiency significantly. Acidic condition of aqueous solution accelerates the process. At pH 2, a reduction of 86.2% was achieved with the absorbed dose of 15 kGy, while, with the same dose, at pH 5 and 7, the …reduction of Cr(VI) were only 36.3% and 22.2%, respectively. Ethanol (0.1% in V:V) and sodium carbonate (1 mmol/L) were added into the solution respectively as relatively non-toxic hydroxyl radical scavengers. Reduction rate increased greatly in the presence of ethanol at each pH. Reduction efficiency of Cr(VI) was enhanced in neutral condition with the addition of sodium carbonate, however, no enhancement was found in acidic condition. The reduction of Cr(VI) was restrained when the solution was saturated with oxygen; however, the restraint was not significant. Show more

Keywords: γ-irradiation, radiation-induced reduction of Cr(VI), hydroxyl radical scavengers, kinetics

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 254-258, 2006

Authors: ZHANG, Bo | CHEN, Jin-long | WANG, Fan | ZHANG, Wei-ming | ZHANG, Quan-xing

Article Type: Research Article

Abstract: This paper presents lab-scale experiment carried out to evaluate the correlation between ammonia nitrogen (NH_3 -N) and p-toluidine using sequencing batch reactor treating synthetic p-toluidine wastewater. The profiles of NH_3 -N and p-toluidine were traced under the concentration of sucrose in the influent varied from 0 to 500 mg/L, aerated airflow varied from 0.6 to 1.2 L/min and temperature varied from 10 to 25°C, respectively. The results showed that the concentration of …NH_3 -N turned from increase to decrease when p-toluidine was nearly completely biodegraded, so the profile of NH_3 -N could clearly indicate the endpoint of p-toluidine biodegradation. And the profile of NH_3 -N was not influenced by the sucrose in the influent, aerated airflow and temperature. It is showed that using ammonia nitrogen as monitoring and control parameter is feasible and reliable and has promising application in amine wastewater treatment by SBR. Show more

Keywords: sequencing batch reactor, correlation, ammonia nitrogen, p-toluidine, biodegradation

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 259-262, 2006

Authors: Batayneh, Awni T. | Qassas, Hani A.

Article Type: Research Article

Abstract: The demand for water resources in the area south of the Dead Sea due to continued development, especially at the Arab Potash Company (APC) for production and domestic purposes necessitates that water quality in the area be monitored and evaluated based on the local geology and hydrogeology. The objective of this paper is to monitor seasonal fluctuations of groundwater and to determine how fluctuation in the water levels will affect the groundwater quality. Groundwater levels were …found to be influenced by rainfall and pumping of water from the wells for domestic and industrial use. Twenty water samples were collected from different wells and analyzed for major chemical constituents both in pre- and post-seasons to determine the quality variation. Chemical constituents are significantly increased after post-season recharge. According to the overall assessment of the area, water quality was found to be useful for drinking, irrigation and industry. Show more

Keywords: water level fluctuations, seasonal variations, quality, Dead Sea coastal aquifers, Jordan

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 263-269, 2006

Authors: HAO, Qing-ju | WANG, Yue-si | SONG, Chang-chun | HUANG, Yao

Article Type: Research Article

Abstract: Wetlands at the interface of the terrestrial and aquatic ecosystems are intensive sites for mineralization of organic matter, but the contribution of winter season fluxes of CH_4 , CO_2 and N_2 O from wetland ecosystems to annual budgets is poorly known. By using the static opaque chamber and GC techniques, fluxes of CH_4 , CO_2 and N_2 O at two freshwater marshes in the Sanjiang Plain were measured …during the winter seasons of 2002/2003 and 2003/2004 with contrasting snow conditions and flooding regimes. The results showed that there were significant interannual and spatial differences in CH_4 , CO_2 and N_2 O fluxes. The Carex lasiocarpa marsh emitted more CH_4 and CO_2 while absorbed less N_2 O than the Deyeuxia angustifolia marsh during the winter seasons. Over the winter season, emissions of CH_4 , CO_2 and N_2 O ranged from 0.42 to 2.41 gC/m^2 , from 24.13 to 50.16 gC/m^2 , and from −25.20 to −148.96 mgN/m^2 , respectively. The contributions of winter season CH_4 and CO_2 emission to the annual budgets were 2.32%–4.62% and 22.17%–27.97%, respectively. Marshes uptake N_2 O during the freezing period, while release N_2 O during the thawing period. The winter uptake equaled to 13.70%–86.69% of the growing-season loss. We conclude that gas exchange between soil/snow and the atmosphere in the winter season contributed greatly to the annual budgets and cannot be ignored in a cool temperate freshwater marsh in Northeast China. Show more

Keywords: freshwater marsh, winter flux, greenhouse gas emission, Sanjiang Plain

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 270-275, 2006

Authors: GUO, Yu-fang | YE, Dai-qi | CHEN, Ke-fu

Article Type: Research Article

Abstract: A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3 . The toluene removal efficiency …decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD (dielectric barrier discharge) with Co_3 O_4 /Al_2 O_3 /foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO_2 when oxygen was more than 5%. Show more

Keywords: dielectric barrier discharge (DBD), plasma, oxygen content, catalyst, toluene, product analysis

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 276-280, 2006

Authors: ZHAO, Yi | XU, Pei-yao | FU, Dong | HUANG, Jian-jun | YU, Huan-huan

Article Type: Research Article

Abstract: Simultaneous removal of SO_2 and NO from flue gas by the highly active absorbent prepared from fly ash, lime and a few oxidizing manganese compound additive was studied using a flue gas circulating fluidized bed (CFB) under different experimental conditions. The effects influencing the removal effiencies were discussed. The optimal flue gas temperature, flue gas humidity, gas velocity of CFB and Ca/(S+N) molar ratio with this process were approximately 110°C, 6%, 1.8 m/s and …1.05, respectively. Removal efficiencies of 92.3% for SO_2 and 60.88% for NO were obtained under the optimal experimental conditions. While the spent absorbent appeared in the form of dry powder, the mechanism of removal for SO_2 and NO based on the highly active absorbent was investigated by a scanning electron microscope (SEM), a X-ray energy spectrometer and the chemical analysis methods. The valuable references can be provided for industrial application by the process. The foreground of application will be vast in China and in the world. Show more

Keywords: simultaneous desulfurization and denitrification, CFB, removal efficiency, mechanism

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 281-286, 2006

Authors: LIU, Wen-ju | Kim, Kyoung-woong | ZHU, Yong-guan | LEE, Sang-woo | CHANG, Pei-chun | Kwak, Ji-hyun

Article Type: Research Article

Abstract: This research includes two investigations. The first one is a market basket survey of the levels of arsenic (As) and trace elements in bracken fern (Pteridium aquilinum) originated from three countries: South Korea, China and North Korea. The results showed that the mean As concentrations in stems of samples were significantly higher than those in leaves. As concentrations in all samples did not exceed food safety limits for vegetables. Generally, concentrations of Fe, Mn, Cu and …Zn in leaves were higher than those in stems. The second investigation is a survey on the levels of As and other heavy metals in vegetation in the vicinity of Myoungbong mine tailings. The results demonstrated that As, Pb and Cu concentrations and bioaccumulation factors (BCF) in seedlings of the fern (Asplenium achilleifolium) were the highest, whereas Marsh horsetail (Equisetum palustre) accumulated the highest levels of Zn. Concentrations of As, Pb, Zn and Cu in vegetable-cress (Lepidium sativum) and the edible herb-aromatic madder (Elasholtzia splendens) were higher than food safety limits. Therefore, a risk assessment of As and other heavy metals in vegetables and herbs on local human health should be conducted in the future. Show more

Keywords: arsenic, heavy metals, ferns, bioaccumulation factors

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 287-291, 2006

Authors: FENG, Xiong-han | ZU, Yan-qun | TAN, Wen-feng | LIU, Fan

Article Type: Research Article

Abstract: Oxidation of As(III) by three types of manganese oxides and the effects of pH, ion strength and tartaric acid on the oxidation were investigated by means of chemical analysis, equilibrium redox, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Three synthesized Mn oxide minerals, birnessite, cryptomelane, and hausmarnite, which widely occur in soil and sediments, could actively oxidize As(III) to As(V). However, their ability in As(III)-oxidation varied greatly depending on their structure, …composition and surface properties. Tunnel structured cryptomelane exhibited the highest ability of As(III) oxidation, followed by the layer structured birnessite and the lower oxide hausmannite. The maximum amount of As(V) produced by the oxidation was in the order (mmol/kg) ofcryptomelane (824.2) > birnessite (480.4) > hausmannite (117.9). As pH increased from the very low value (pH 2.5), the amount of As(III) oxidized by the tested Mn oxides was firstly decreased, then negatively peaked in pH 3.0–6.5, and eventually increased remarkably. Oxidation of As(III) by the Mn oxides had a buffering effects on the pH variation in the solution. It is proposed that the oxidative reaction processes between As(III) and birnessite (or cryptomelane) are as follows: (1) at lower pH condition: (MnO_2 )_x + H_3 AsO_3 + 0.5H^+ =0.5H_2 AsO_4^- +0.5HAsO_4^{2-} +Mn^{2+} +(MnO_2 )_{x-1} + H_2 O; (2) at higher pH condition: (MnO_2 )_x + H_3 AsO_3 – 0.5H_2 AsO_4 +0.5HAsO_4^{2-} +1.5H^+ + (MnO_2 )_{x-1} ·MnO. With increase of ion strength, the As(III) oxidized by bimessite and cryptomelane decreased and was negatively correlated with ion strength. However, ion strength had little influence on As(III) oxidation by the hausmannite. The presence of tartaric acid promoted oxidation of As(III) by birnessite. As for cryptomelane and hausmannite, the same effect was observed when the concentration of tartaric acid was below 4 mmol/L, otherwise the oxidized As(III) decreased. These findings are of great significance in improving our understanding of As geochemical cycling and controlling As contamination. Show more

Keywords: oxidation of As(III), As(V), Mn oxides, pH, ion strength, tartaric acid

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 292-298, 2006

Authors: FAN, Xiao-hui | SONG, Yong-sheng | LIN, De-xi | YANG, Lin-zhang | LUO, Jia-fa

Article Type: Research Article

Abstract: Ammonia volatilization loss and ^{15} N balance were studied in a rice field at three different stages after urea application in Taihu Lake area with a micrometeorological technique. Factors such as climate and the NH_4^+ -N concentration in the field floodwater affecting ammonia loss were also investigated. Results show that the ammonia loss by volatilization accounted for 18.6%–38.7% of urea applied at different stages, the greatest loss took place when urea was applied at …the tillering stage, the smallest at the ear bearing stage, and the intermediate loss at the basal stage. The greatest loss took place within 7 d following the fertilizer application. Ammonia volatilization losses at three fertilization stages were significantly correlated with the ammonium concentration in the field floodwater after the fertilizer was applied. ^{15} N balance experiment indicated that the use efficiency of urea by rice plants ranged between 24.4% and 28.1%. At the early stage of rice growth, the fertilizer nitrogen use efficiency was rather low, only about 12%. The total amount of nitrogen lost from different fertilization stages in the rice field was 44.1%–54.4%, and the ammonia volatilization loss was 25.4%–33.3%. Reducing ammonia loss is an important treatment for improving N use efficiency. Show more

Keywords: ammonia volatilization, urea, ^{15}N balance, rice, influence factors, Taihu region

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 299-303, 2006

Authors: SUN, Bing-yao | TAN, Jian-zhong | WAN, Zhi-gang | GU, Fu-gen | ZHU, Ming-de

Article Type: Research Article

Abstract: To investigate the potential role of allelopathy in plant interference and in the successful invasion of alien species Solidago canadensis, aqueous and ethanolic extracts from rhizomes, stems and leaves of S. canadensis were prepared and used as treatment solutions to assess their effects on seed germination and seedling growth in four target species, mulberry (Morus alba); morning glory (Pharbitis nil), wheat (Triticum aestivum) and rape (Brassica campestris). Reduction and/or growth in germination and …growth of the target plant species in the presence of both aqueous and ethanolic extracts at different concentrations indicated that the responses were species-specific and concentration-dependent. Generally, ethanolic extracts (especially from leaves) imposed stronger effects on both seed germination and seedling growth. Extracts with lower concentration at 0.001 g/ml dw could stimulate the seedling growth of rape and morning glory, whereas extracts at any given concentrations have inhibitory effects on wheat and mulberry. It is suggested that the aqueous and ethanolic extracts of all the three parts of S. canadensis have significant allelopathic effects. Although both inhibition and stimulation occurred in the germination and growth of the target species, extracts with higher concentrations definitely inhibit seed germination and seedling growth of all target plants. We suggest that allelopathy plays a more important role than other mechanisms do in the out-competition of S. canadensis over other plants, and make it invasive in new habitats. Show more

Keywords: Canada goldenrod (Solidago canadensis L.), allelopathy, extracts, seed germination, seedling growth

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 304-309, 2006

Authors: SONG, Xue-ying | SONG, Yu-fang | SUN, Tie-heng | ZHOU, Qi-xing | ZHANG, Wei | ZHANG, Lei

Article Type: Research Article

Abstract: Five dominant bacteria strains (Acetobacter sp., Alcaligenes sp., Micrococcus sp., Arthrobacter sp. and Bacillus sp.) and five fungi strains (Cephalosporium sp. I, Cephalosporium sp. II, Aspergillus sp. I, Aspergillus sp. II and Fusarium sp.) isolated from petroleum-contaminated soil were used to assess the potential capability of mineral oil and PAH enhanced degradation separately and jointly using the batch liquid medium cultivation with diesel oil spiked at 1000 mg/L. The experiment was performed on a reciprocal shaker …in the darkness at 25°C to 30°C for 100 d. The dynamic variation in the activity of microbial inoculators in each treatment and the degradation of the target pollutants during the period of experiment were monitored. Results showed a more rapid biodegradation of mineral oil and PAHs at the beginning of the experiment (about 20 d) by dominant bacteria, fungi and their mixture than that of the indigenous microorganisms, however, thereafter an opposite trend was exhibited that the removal ratio by indigenous microorganisms was superior to any other dominant treatments and the tendency lasted till the end of the experiment, indicating the limited competitive capability of dominant microorganisms to degrade the contaminants, and the natural selection of indigenous microorganisms for use in the removal of the contaminants. At the end of the experiment, the removal ratio of mineral oil ranged from 56.8% to 79.2% and PAHs ranged from 96.8% to 99.1% in each treatment by microbial inoculators. Show more

Keywords: dominant microorganism, indigenous microorganism, mineral oil, PAHs, biodegradation

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 310-317, 2006

Authors: MASKAOUI, Khalid | HU, Zhong | ZHOU, Jun-liang | HAN, Ya-li

Article Type: Research Article

Abstract: An intensive investigation was conducted to study the distribution of polycyclic aromatic hydrocarbons (PAHs), to show firstly the level of pollution in the agricultural areas and analyses specifically the status of soil polluted by these persistent pollutants in some locations of Xiamen region. Soil samples collected from Jiulong agricultural catchment have been analysed for 16 PAH compounds, using gas chromatography flame ionization detection in order to determine the level of selected PAH components and to …identify the factors that may control their distribution and persistence in the area. The main PAHs found in soil samples were the low molecular weight. The total PAHs detected in soil samples ranged from 0.50 to 0.95μg/g soil. The highest values of PAHs were significantly detected in the orange tree leaves, which range from 236.1 to 249.3μg/g soil showing recent atmospheric inputs of these volatile pollutants. The distribution of PAHs in vegetable were monitored and indicating that the concentration were high and ranged from 8.24 to 58.87μg/g. Other sediment samples were also collected and analysed from urban sewage (5.26μg/g dw), aquacultura (0.52μg/g dw) and industrial areas (from 0.62 to 2.09μg/g dw), during this investigation. The contamination of Jiulong river estuary and Xiamen Western Sea by PAHs has been then widely justified by wastewater discharges and soil runoffs from these areas. The results, therefore, provide important information on the current contamination status caused by the atmospheric transport and point to the need for urgent actions to stop the release of these hydrocarbons to the environment. The necessity of implementing systematic monitoring of PAHs is also emphasized. Show more

Keywords: PAHs, soil, Jiulong River Estuary, Xiamen Western Sea

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 318-322, 2006

Authors: LI, Qi | JIANG, Yong | LIANG, Wen-ju

Article Type: Research Article

Abstract: The influence of Cu and Zn on soil nematode communities was examined along a pollution gradient with increasing distance from a metallurgical factory. Total and available heavy metal contents were used to study the effects of heavy metals on nematode abundance, trophic groups and ecological indices. The results demonstrated significant correlations between the number of total nematodes, bacterivores, plant-parasites and the total and available heavy metals. Bacterivores and plant-parasites were the dominant trophic …groups. Significant differences in different sampling sites were found only in the number of bacterivores (P<0.0l). The Shannon-Weaver diversity index (H'), trophic diversity index (TD), evenness index (J') and dominance index (λ) were found to be sensitive to soil pH and C/N ratios. Significant correlations were found between the total nematodes (TNEM), some genera (Acrobeloides, A phelenchoides, Cephalobus, Ditylenchus, Mesorhabditis, Tetylenchus and Tylenchus) and distance from the factory. Show more

Keywords: soil nematodes, trophic groups, ecological indices, heavy metals, metallurgical factory

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 323-328, 2006

Authors: ZHANG, Ming-kui | FANG, Li-ping | HUANG, Chang-yong

Article Type: Research Article

Abstract: Heavy metals can be introduced into urban soils at the same time. Therefore, their selective retention and competitive adsorption by the soils become of major importance in determining their availability and movement throughout the soil. In this study, the availability and mobility of six heavy metals in eight urban soils collected from different cities of Zhejiang Province, southeastern China were assessed using distribution coefficients (Kd) and retardation factor (Rf). The results showed that there were great …differences in the Kd and Rf among the tested soils. The adsorption sequences were Cr>Pb>Cu>Cd>Zn>Ni, and the Kd decreased with increasing levels of metal addition. Ni generally has the lowest Rf values followed closely by Cd, and Zn whereas Cr and Pb reached the highest values. The results suggest that Ni and Zn have the highest mobility associated to the lowest adsorption, Cr and Pb present the opposite behavior. Correlation analysis indicates that soil pH, CaCO_3 content, and cation exchange capacity (CEC) are key factors controlling the solubility and mobility of the metals in the urban soils. Show more

Keywords: competitive adsorption, mobility sequence, heavy metal, urban soil

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 329-333, 2006

Authors: LI, Yu-hong | YAN, Chong-ling | YUAN, Jian-jun | LIU, Jing-chun | CHEN, Huai-yu | HU, Jun

Article Type: Research Article

Abstract: In order to investigate distributions of heavy metal pollution in Quanzhou Bay wetland, the total concentration and chemical partitioning of a number of heavy metals (Cu, Zn, Cd, Pb, Cr, Hg) in sediments of three sampling sites of Quanzhou Bay wetland and their availability to Suaeda australis were analyzed. The Geoaccumulation Index (I_{geo} ) values reveal that the sediments of three sampling sites may all be considered as moderately contaminated for Pb and Zn, and …all sediments might be strongly contaminated with cadmium. The partitioning analyses revealed the measured heavy metals in three sites are bound to the exchangeable fraction at lower concentrations. The measured metals in a considerable amount are bound to the reducible and oxidizable fractions, and a high proportion of the measured heavy metals were distributed in the residual fraction in the sediment samples. The concentrations of Cd in each chemical phase extracted from the sediments are above natural global background levels and should be further investigated because of its toxicity. Suaeda australis has different accumulation abilities for the measured heavy metals. For the root and stem, the bioaccumulation ability assessed by bioaccumulation factor (BA F) for the measured heavy metals follows the decreasing order as: Cu>Cr>Zn>Cd, Pb, Hg. In the leaf, stronger bioaccumulation ability for Hg is exhibited. The heavy metal concentrations in Suaeda australis roots have positive correlations with their available fractions, while the exchangeable fraction of Cu and Cd might have be more important to both mature plant roots and seedling roots uptake than other fractions; as for Cr, the oxidizable fraction might make a greater contribution to the plant root uptake; as for Zn, the reducible fraction might make so contribution; and for Pb, the oxidizable fraction might make a significant contribution to the mature plant root uptake, however, the exchangeable fraction might have a significant contribution to the seedling root uptake. Show more

Keywords: bioavailability, geoaccumulation factor, partitioning, heavy metals, Suaeda austrdis, sediment, Quanzhou Bay wetland

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 334-340, 2006

Authors: LI, Li-jun | LIU, Xue-mei | DUAN, Yi-hao | GUO, Ya-ping | CHENG, Bin | GUO, Jun | XI, Yu-ying | MA, En-bo

Article Type: Research Article

Abstract: One purpose of this research is to present accumulation of cadmium (Cd) and copper (Cu) by female Oxya chinensis (Orthopera: Acridoidea) in a simulated soil-plant-insect ecosystem treated with Cd. Fourth-instar nymphs of O. chinensis had been fed on wheat (Triticum aestivum) seedlings contaminated with Cd and Cu for one month. In the ecosystem, the Cd concentration in wheat seedlings rose greatly with the increasing of Cd in the soil, but the Cu concentration in wheat seedlings …was not found elevated. There was a highly significant difference (P<0.05) in Cd concentrations of wheat seedlings and not any significant difference (P>0.05) in Cu concentrations of wheat seedlings. The Cd and Cu concentration in different body part-head, thorax, abdomen, and hind femur, varied under different Cd concentrations in soil. There were significant differences (P<0.05) in the four parts of Cd and Cu accumulations with all treatments. The order of Cd accumulation was thorax >abdomen >head >hind femur and the Cu was abdomen > thorax > head > hind femur. The results indicated that Cd and Cu were accumulated from the soil to grasshoppers through the plant; that is to say, Cd and Cu in environment could be transported to animal or human via food chain. Show more

Keywords: accumulation, cadmium (Cd), copper (Cu), grasshopper (Oxya chinensis), soil-plant-insect ecosystem

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 341-346, 2006

Authors: YU, Xiao-zhang | LEI, Jun-jie | XUE, Nan-dong | TANG, Ya-wen

Article Type: Research Article

Abstract: Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. Hybrid willows (Salix matsudana Koidz × Salix alba L.) were exposed to cyanide to determine whether willows can transport and metabolize this compound. Pre-rooted trees were grown in different environmental compartmentsspiked or irrigated with potassium cyanide at 24.0±0.5°C. Cyanide in compartments, in air and in tissues of plants was analyzed spectrophotometrically. Results from this study indicated …that large amounts of applied cyanide was removed from the systems during the presence of willows. Growing compartments of plants have a strong influence on the removal rates of cyanide. Little or no initial cyanide was detected in plant materials. Volatilization of cyanide was not occurring. Mass balance studies showed that applied cyanide was significantly metabolized during transport through willows cuttings. However, there was a clear difference between the metabolism rates of cyanide by willows exposed to different environmental compartments. The highest cyanide metabolism rate was found at the treatment with willows growing in hydroponic solution with a metabolism rate of 2.44 mgCN/(kg·d), followed by willows growing in sand with a value of 1.02 mgCN/(kg·d), The lowest metabolism rate had the willows growing in soils (0.43 mg CN/(kg·d)). In conclusion transport and metabolism of cyanide in plants is likely and phytoremediation of cyanide is a feasible option for cleaning soils and water contaminated with cyanide. Show more

Keywords: cyanide, hybrid willows, metabolism, phytoremediation

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 347-352, 2006

Authors: YU, Juan | TANG, Xue-xi | TIAN, Ji-yuan | ZHANG, Pei-yu | DONG, Shuang-lin

Article Type: Research Article

Abstract: Effects of elevated CO_2 (5000μl/L) on sensitivity comparison of six species of algae and interspecific competition of three species of algae were investigated. The results showed that, the cell densities of six species of algae grown in elevated CO_2 significantly increased compared to those in ambient CO_2 (360μl/L), and with the time prolonged, the increasing extent increased. Therefore, elevated CO_2 can promote the growth of …six species of algae. However, there were differences in sensitivity between six species of algae. Based on the effects of elevated CO_2 on biomass, the sensitive order (from high to low) was Platymanas sp., Platymanas subcordiformis, Nitzschia closterium, Isochrysis galbana Parke 8701, Dunaliella salina, Chlorella sp., on the condition of solitary cultivation. Compared to ambient CO_2 , elevated CO_2 promoted the growth of three species of algae, Platymanas subcordiformis, Nitzschia closterium and Isochrysis galbana Parke 8701 under the condition of mixed cultivation. The sensitivity of the three species to elevated CO_2 in mixed cultivation changed a lot compared to the condition of solitary cultivation. When grown in elevated CO_2 under the condition of mixed cultivation, the sensitive order from high to low were Nitzschia clostertium, Platymonas subcordiformis and Isochrysis galbana Parke 8701. However, under the condition of solitary cultivation, the sensitive order in elevated CO_2 was Isochrysis galbana Parke 8701, Nitzschia clostertium, Platymonas subcordiformis, from sensitive to less sensitive. On the day 21, the dominant algae, the sub-dominant algae and inferior algae grown in elevated CO_2 did not change. However, the population increasing dynamic and composition proportion of three algal species have significantly changed. Show more

Keywords: elevated CO_2, microalgae, sensitivity, interspecific competition

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 353-358, 2006

Authors: ZHENG, Rong-hui | WANG, Chong-gang | ZUO, Zheng-hong | CHEN, Yi-xin | ZHAO, Yang

Article Type: Research Article

Abstract: Tributyltin (TBT), an organometal used as an antifouling biocide, has been reported to induce masculinization of fish. Benzo[a]pyrene (BaP), a widespread carcinogenic polycyclic aromatic hydrocarbon, has been reported that its microsomal metabolites can produce an estrogenic response when tested in vitro. This study was therefore designed to examine the potential in vivo influence of TBT, BaP and their mixture on sex hormone levels in serum of Sebastiscus marmoratus, which were given 2 separate intraperitoneally(ip) …injections (a single injection every 7 d) of TBT (0.5, 1, 5 and 10 mg/kg), BaP (0.5, 1, 5 and 10 mg/kg), or both in combination (0.5, 1, 5 and 10 mg/kg); control fish received olive oil vehicle only. Six days after the 2nd injection, serum samples were collected and analyzed for sex hormone levels and alkali labile protein phosphorus (ALPP), which is related to the yolk precursor protein vitellogenin. The pollutants at all doses significantly reduced serum testosterone, estradiol and ALPP content after 2 injections compared with the corresponding controls. The reduction of the estradiol levels should be response for the decrease of the vitellogenin levels. The results in the present study suggested that aromatase seems not the major target acted by TBT and BaP in fish. This study demonstrated that TBT or BaP exposure both inhibit the reproductive potential in female Sebastiscus marmoratus. Combined effect of TBT and BaP on the serum testosterone, estradiol and ALPP was not antagonism from the anticipation. Show more

Keywords: tributyltin, benzo[a]pyrene, estosterone, 17β-estradiol, vitellogenin, Sebastiscus marmoratus

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 359-363, 2006

Authors: DAKA, Erema Ransome

Article Type: Research Article

Abstract: The population of the intertidal gastropod Littorina saxatilis from Laxey estuary in the Isle of Man is exposed to mine-related contamination of Zn (and is tolerant to Zn and Pb) compared to those of Castletown, Derbyhaven, Peel and Ramsey. Tolerances to salinity and desiccation stress were assayed to test how metal tolerance could affect tolerance to general stress. The winkles were experimentally exposed to salinities of 0, 17 and 60 practical salinity units (psu) with 34 …psu as control. Desiccation stress was determined by aerial exposure of the winkles at 24°C. No control mortalities were recorded and mortalities in 17 psu were less than 50% for all populations over a 24-day exposure period. LT_{50} values (mean ± SD, n=5) at 0 psu ranged from 6.6±0.6 to 7.5±1.3 d for winkles from Ramsey and Laxey respectively. The values for 60 psu ranged from 7.0 ±0.7 to 8.4 ±0.9 d. No significant differences in LT_{50} values were obtained for the salinity exposures (ANOVA, P>0.05) but there was a significant difterence in tolerance to desiccation (P<0.01). The winkles from Laxey showed very high susceptibility to desiccation stress probably indicating a physiological trade-off to metal tolerance. Show more

Keywords: tolerance, salinity, desiccation, winkles, Isle of Man

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 364-368, 2006

Authors: ZHANG, Ya-lei | ZHANG, Zhi-gang | XU, De-qiang | QIANG, Zhi-min | LI, Guang-ming | ZHAO, Jian-fu

Article Type: Research Article

Abstract: 2,6-Ditert-butylphenol (2,6-DTBP) is a major organic contaminant presenting in acrylic fiber manufacturing wastewaters. This compound is of high bio-resistance due to its complex structure which consists of one phenol group and two highly branched tert-butyl groups. This research attempted to improve the biodegradation efficiency of 2,6-DTBP through various strain immobilization methods. The stratified immobilization can settle oxygen transmission in the single microorganism immobilization, and can realize two-process reaction in the single device …by choosing two symbiotic microorganisms. Two effective strains, named F-l-4 and F-3-4, which were screened out in our previous work, were used to degrade 2,6-DTBP after being immobilized in calcium alginate gel. Results indicate that the substrate removal efficiency of various immobilization methods follows the order: stratified > single F-3-4> mixed ≈ single F-1-4. The immobilized biodegradation capacity was higher than the free one. After an incubation time of 12 d, 91% of 2,6-DTBP could be degraded by the stratified immobilization method, compared to 79% achieved by the mixed immobilization method with an initial 2,6-DTBP concentration of 100 mg/L. The stratified immobilization satisfies the oxygen demand nature of the aerobic F-3-4 and the facultative F-1-4, thus yielding the highest degradation efficiency. Both the outer layer strain F-3-4 and the inner layer strain F-1-4 can grow actively on the substrate of 2,6-DTBP, as illustrated by SEM images. This study shows that the highly bio-refractory compound, 2,6-DTBP, can be effectively degraded using appropriately immobilized microorganism strains. Show more

Keywords: biodegradation, 2,6-ditert-butylphenol, immobilization, microorganism strains

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 369-372, 2006

Authors: YE, Yang-fang | MIN, Hang | LÜ, Zhen-mei

Article Type: Research Article

Abstract: The effect of acetanilide herbicide mefenacet on soil microbial communities was studied using paddy soil samples with different short-term treatments. The culturable bacteria (plate counts), dehydrogenase activity and changes in community structure(denaturing gradient gel electrophoresis (DGGE) analysis) were used for biological community assessments. Mefenacet was a significant stimulus to cultural aerobic bacteria and dehydrogenase activity while Sphingobacterium multivorum Y1, a bacterium efficiently degrading the mefenacet, only induced the increasing colony-forming unit (CFU) …of bacteria but little effect on dehydrogenase activity during the whole experiment. The degree of similarity between the 16S rDNA profiles of the communities was quantified by numerically analyzing the DGGE band patterns. Similarity dendrograms showed that the microbial community structures of the mefenacet-treated and non-treated soils were not significantly different. But supplement ofS. multivorum Y1 could increase the diversity of the microbial community in the mefenacet-polluted paddy soil. This work is a new attempt to apply the S. multivorum Y1for remediation of the mefenacet-polluted environments. Show more

Keywords: denaturing gradient gel electrophoresis (DGGE), soil microbial diversity, mefenacet, dehydrogenase

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 373-378, 2006

Authors: XU, Wen-ying | FAN, Jin-hong | GAO, Ting-yao

Article Type: Research Article

Abstract: The reduction of the nitrobenzene compounds (NBCs) by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium (pH=11). The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder's iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order: nitrobenzene >4-chloro-nitrobenzene m-dinitrobenzene >4-nitrophenol 2,4-dinitrotoluene >2-nitrophenol. The reduction …rate by Master Builder's iron decreased in the following order: m-dinitrobenzene 4-chloro-nitrobenzene >4-nitrophenol >2,4-dinitrotoluene ≈nitrobenzene >2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe(OH)_2 in Master Builder's iron. It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC's electron withdrawing ability. Show more

Keywords: wastewater contaminated by NBCs, electrochemical reduction characteristics, catalyzed Fe-Cu process, reduction mechanism

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 379-387, 2006

Authors: CHEN, Lin | ZHOU, Ming-hua | LEI, Le-cheng

Article Type: Research Article

Abstract: This paper provides evidence for the degradation of organic pollutant by the photo-Fenton complex mechanism. Both the complex oxidation and HO· oxidation mechanisms were verified by p-chlorophenol degradation, UV/Vis spectra anaylsis, and quantum yield. The hydroxyl radical involved in the photo-Fenton process can also be generated from the decomposition of H_2 O_2 , photolysis of Fe^{3+} and degradation of hydrated Fe(VI)-complex, excepting the traditional Fenton reaction.

Keywords: photo-Fenton, p-chlorophenol, mechanism

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 388-391, 2006

Authors: ZHU, Xi-feng | ZHENG, Ji-lu | GUO, Qing-xiang | ZHU, Qing-shi

Article Type: Research Article

Abstract: The paper is focused on studying how to convert rice husk and sawdust into liquid fuel. Rice husk, sawdust and their mixture were pyrolyzed at the temperature between 420°C and 540°C, and the main product of liquid fuel was obtained. The experimental result showed that the yield of liquid fuel heavily depended on the kind of feedstock and pyrolysis temperature. In the experiments, the maximum liquid yields for rice husk, sawdust and their mixture were 56% …at 465°C, 61% at 490°C and 60% at 475°C respectively. Analysis with GC-MS and other apparatus indicated that the liquid fuel is a complicated organic compound with low caloric value and can be directly used as fuel oil without any up-grading. As a crude oil, the liquid fuel can be refined to be vehicle oil. Show more

Keywords: solid organic waste, rice husk, sawdust, pyrolysis, liquid fuel

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 392-396, 2006

Authors: LU, Jian-wei | LI, Fang-bai | GUO, Ting | LIN, Lan-wen | HOU, Mei-fang | LIU, Tong-xu

Article Type: Research Article

Abstract: TiO_2 and l%Ce^{3+} -TiO_2 prepared by hydrothermal method were characterized by means of XRD and UV-visible diffusive reflectance spectra (DRS). The results of DRS analysis indicated that the 1%Ce^{3+} -TiO_2 catalyst had significant optical absorption in the visible region between 400–450 nm because electrons could be excited from the valence band of TiO_2 or cerium oxides to Ce 4f level. To investigate …the photocatalytic activity of different catalysts for crop fungal disease control, a series of Quine tests were carried out for cucumber powdery mildew and litchi downy blight control in home-made photocatalytic reactor. The results showed that TiO_2 photocatalysis technique should be effective to inhibit the growth of fungal diseases to some extent and P-25 had a higher activity for antifungal control than home-made TiO_2 catalysts. TiO_2 -A prepared with Ti(SO_4 )_2 is more active to contro 1 antifungal disease than TiO_2 -B prepared with TiOSO_4 as precursor because the crystalline of TiO_2 -A was higher than that of TiO_2 -B. The antifungal index litchi downy blight control was greatly enhanced by doping 1% cerium ion. The antifungal index of 1.0%Ce^{3+} -TiO_2 was (47.0±4.7)%, (82.2±3.5)%, (100±0.0)% under indoor weaker light, solar light and black light, respectively. The results of field experiments showed that the antifungal index of 1.0%Ce^{3+} -TiO_2 was more than that of P-25. The antifungal index of 1.0%Ce^{3+} -TiO_2 was (81.7 ±6.5)%, (67.5 ±4.7)%, (38.6 ±1.9)% for litchi downy blight, maize southern leaf spot, and rice blast, respectively. It was concluded that TiO_2 photocatalysis technique should be an effective way for litchi fungal disease control in practice. Show more

Keywords: titanium dioxide, photocatalytic, fungal disease, solar light, litchi downy blight

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 397-401, 2006

Authors: YAO, Shu-chun | XUE, Bin | XIA, Wei-lan

Article Type: Research Article

Abstract: Vertical profiles of the total organic carbon (TOC), total nitrogen (TN), phosphorus, susceptibilities, elements and partical size were analyzed in a short ^{137} Cs-dated sediment core collected from Honghu Lake, China. The average sedimentation rate was 1.55 mm/a. The results indicated that trophic status of Honghu Lake in the historical period had experienced three stages. Before 1840 the lake was characterized with lower productivity, TOC was less than 9.92 g/kg; TN was 0.902 to 1.24 …g/kg. During about 1840–1950, population increased quickly, there was an obvious change in TOC with an average of 13.0 g/kg. Since 1950, human impacts have accelerated the lake eutrophication and nutrients enriched in the sediment with TOC of 21.7 to 93.1 g/kg, TN of 1.77 to 8.78 g/kg. The heavy metal concentration profiles presented similar distribution trends except Pb and Mn. The results from elements analyses indicated that Honghu Lake had not been polluted by heavy metals except lead. Show more

Keywords: Honghu Lake, lake deposit, human impact

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 402-406, 2006

Authors: NI, Ming-jiang | XIAO, Gang | CHI, Yong | YAN, Jian-hua | MIAO, Qi | ZHU, Wen-li | CEN, Ke-fa

Article Type: Research Article

Abstract: In order to develop municipal solid waste (MSW) pyrolysis/gasification and melting technology with low emission and high efficiency, it was planed that all the main components in MSW and some typical kinds of MSW were pyrolyzed/gasified to propose an expert system for raw MSW. In this paper, wood, which was a prevalent component in MSW, was pyrolyzed and gasified in fluidized-bed reactors at different apparent excess air ratios (EARs), temperatures and fluidizing velocities. For pyrolysis, with …temperature increasing from 400°C to 700°C, the yield of pyrolysis char decreased while that of pyrolysis gas increased (in this paper respectively from 28% to 20% and from 10% to 35%), and when temperature was 500°C, the yield of pyrolysis tar reached the highest, up to 38% in this paper. It was the optimum for gasification when temperature was 600°C and apparent EAR was 0.4. Under the experimental conditions of this paper, gasification efficiency achieved 73%, lower heat value (LHV) reached 5800 kJ/(Nm^3 ) and yield of syngas was 2.01 Nm^3 /kg. Lower fluidizing velocity was useful to upgrade gasification efficiency and LHV of syngas for wood gasification. Based on the results, the reactive courses and mechanism were analyzed respectively for wood pyrolysis and gasification. Show more

Keywords: wood, pyrolysis, gasification, municipal solid waste(MSW)

Citation: Journal of Environmental Sciences, vol. 18, no. 2, pp. 407-415, 2006